To date, transistors used in power electronic applications have typically been fabricated with silicon (Si) semiconductor materials. Common transistor devices for power applications include Si CoolMOS, Si Power MOSFETs, and Si Insulated Gate Bipolar Transistors (IGBTs). Compound semiconductors, for example III-V compound semiconductors such as GaAs are also useful in some applications. More recently, silicon carbide (SiC) power devices have been considered. Group III-N-based semiconductor devices, such as gallium nitride (GaN)-based devices, are now emerging as attractive candidates to carry large currents, support high-voltages and to provide very low on-resistance and fast switching times.